Field
The present disclosure relates to a laundry treatment apparatus.
Discussion of the Related Art
A conventional laundry treatment apparatus includes a cabinet forming an appearance of the laundry treatment apparatus, a tub installed in the cabinet, a drum rotatably installed in the tub to wash laundry, and a motor having a rotating shaft coupled to the drum while passing through the tub so as to rotate the drum.
The drum may rotate without the need to maintain a dynamic equilibrium (dynamic balance) depending on a position of laundry disposed therein.
“Dynamic equilibrium” means a state wherein, during rotation of a rotating body, a centrifugal force of the rotating body or a moment created by the centrifugal force becomes zero with respect to the axis of rotation. In the case of a rigid body, dynamic equilibrium is maintained when the mass of the rigid body is evenly distributed about the axis of rotation.
Accordingly, a dynamic equilibrium in a laundry treatment apparatus may be considered as a state where the mass distribution of laundry about an axis of rotation of a drum including laundry contained therein falls within an allowable range during rotation of the drum (a state where the drum rotates within an allowable amplitude range of vibration).
Meanwhile, an unbalanced state, or a state wherein the dynamic equilibrium in a laundry treatment apparatus is lost, means that the mass distribution of laundry about the axis of rotation of a drum is non-uniform during rotation of the drum. Such a loss of dynamic equilibrium occurs when laundry is not evenly distributed along an inner surface of the drum.
When a drum rotates in an unbalanced state, vibration is generated. The vibration of the drum is transmitted to a tub or a cabinet and generates noise.
Conventional laundry treatment apparatuses are typically equipped with a balancer to resolve an unbalanced state of a drum. Balancers incorporated in such conventional laundry treatment apparatuses include ball balancers or fluid balancers in which a ball or fluid is contained in a housing fixed to a drum.
When a drum is in the unbalanced state, the drum exhibits the highest rotational speed when laundry incurring the unbalanced state passes through the lowest point of the rotational orbit of the drum and exhibits the lowest rotational speed when laundry incurring the unbalanced state passes through the highest point of the rotational orbit of the drum.
Therefore, a ball balancer or a fluid balancer incorporated in conventional laundry treatment apparatuses controls an unbalanced state by moving a ball or fluid toward the lowest point of a rotational orbit of a drum when laundry incurring the unbalanced state moves toward the highest point of the rotational orbit of the drum.
Although the above-mentioned method of controlling an unbalanced state in a laundry treatment apparatus is useful when the amplitude of a steady state vibration of a drum falls within a predetermined range, satisfactory effects cannot be obtained under the type of transient vibration to which the drum is subjected to before the vibration of the drum reaches the steady state.
Furthermore, conventional balancers experience difficulty in immediately and actively resolving unbalanced states when such unbalance occurs.